WO 95/33343 discloses a projection system for high-definition images. A stack of three transparent LCD displays is illuminated by one light source. The light exiting from the LCD display is concentrated by means of an optical array and projected as a real image onto a screen. Since the images have an optical path length difference when split up between blue, red and green, the difference is compensated before the projection. To do so, dichroitic mirrors are provided that are arranged depending on the structure of the LCD display.
A further display for color images is disclosed in EP-0 458 270 A2. Three light modulators (red, green and blue) are linearly arranged and provided with an optical system connected in series that combines the light from the three light modulators and compensates for the optical path length difference. The optical system comprises several conventional prisms and a dichroitic mirror.
EP-0 431 716 A2 discloses a device permitting a parallax-free projection onto a CRT. The LCD's are arranged in a row. To avoid projection errors in the projection plane, a geometrical correction of the beams is performed. Each LCD is assigned a projection lens that displays on the projection screen the light that passes through the red, green or blue filters and that has been corrected by aligning lenses.